The invention relates more particularly to a motor vehicle disc brake including:                a cover including two tiered bores of parallel axes, each whereof includes at least one first section;        a caliper slidably mounted axially with respect to the cover;        two pins of parallel axes, each whereof includes an axial attachment end attached to the caliper and at least one guiding section for axial sliding of the caliper with respect of the cover which extends from a free end of the associated pin and which is slidably mounted in the first section of the associated tiered bore of the cover.        
In this design, the guiding section of each pin is slidably mounted in the first section of the associated bore which is blind or closed, for the purposes of tightness and protection of this sliding guiding zone, and a quantity of air is thus trapped between the free end of the guiding section of the pin and the base of the first section of the associated bore.
During the axial insertion of the pin into the associated bore on the fitting and assembly line, or during the so-called “de-braking” phase when the disc pushes back the brake pad and the caliper, this volume is reduced by progressive forward motion of the free end of the guiding section of the pin towards the base of the first section of the bore.
So that the volume of air trapped does not impede, or abut against, this forward motion, it is necessary to provide means enabling the progressive evaluation of the trapped air.
The prior art particularly includes a series of solutions requiring modifications, that are complex to carry out, of the tiered bore which further affect the sliding guiding capabilities of the associated pin.